Airedale Easicool Airflow

[Neddy]

Hi Guys,

This unit iced up last week and tripped on frost protection. The call was attented my work mate. He melted the ice and ran it up but found nothing wrong.

Today I got the same call, water on the floor and unit on frost protection alarm.
The Model is a V17X-EZR and the supply air is ducted from the top into the next room and it supplies about eight 600x600 grills with a lot of ducting.
The air flow is quiet poor from the grills.
In the settings the fan speed is set to 75%. Fan speed is set to be reduced by 25% when Dehumidification is activated.Airedale say this it to drag more moisture out of the air. The frost protection is activated when the senor on the evaporator reads a low temperature. I changed the Dehumidification reduced fan speed to 0% as I believe the coil temperature was getting too low due to the reduced air flow on Dehumidification and the coil was icing up.

Airedale say the unit was commissioned at 75% fan speed. My question is, can I put it to 100% to more air flow?

Also this unit has one airflow switch for the fan(Which I wanted to test) and the filters run on a timer and then alarm.
I blocked the filters with cardboard. The airflow switch is set to 1.5 mbar. I adjusted it to 3.5 Mbar and the contacts disconnected. I removed the cardboard but the contacts did not make until I moved the dial to 1.5Mbar.

Can anyone explain what I doing wrong?

[al]

is the return air ducted from the room also? if icing up i'd suspect air flow, what temp difference do you have air on to air off, what pressures/temps and what refrigerant, superheat and subcool?

is the evap coil clean?

al

[Neddy]

Hi Al,

It has a grill in the wall for return air to get back. Couldnt check pressures as the room as a fire extinguisher system which could not be put into manual but my work mate got to check them last week and he said all pressures were ok.

From the controller, the return air was 21 degrees celcius, Coil temp around 8-10 degrees celicus and dropped to 4 when dehum came in as fan speed dropped by 25%.

Head pressure 25-26bar.(R410a)

Coil is spotless unit is less than a year old.

What part of the green land are you from?

[al]

Living in Cork, return at 21 is fine, air off at 10? There should be no need to drop fan speed to dehum, first unit i've heard that does this, i reckon your changing the fan speed may sort it, is humidity an issue and is it controlling humidity ok?

al

[stufus]

Fan speed reduction for dehum is not uncommon Al.
Your just to used to dealing with Edpacs,which we all know do things the cheap way.
Whats the setpoint on the unit neddy? And is the return grille big enough for the required air flow. Has any extra equipment (load) been added to the space.
Cheers
Stu

[al]

Yep, cheap and cheerful edpacs, but does ramping the fan up and down not bugger up the room tempertures?

al

[Neddy]

From Cork myself . I remember working on Edpacs a long time ago.

Hi Stu, setpoint is 18 and unit feeds an Archives room. Nothing in the room yet except racking. Humidity setpoint is 40% and ive seen the Humidity in the room at 45 to 50 percent so the unit runs quiet a bit.
Return air grill is about 2mx1m.

[stufus]

Not really Al because on dehum you're over shooting the cooling setpoint to get the air below dew point so it condenses,slowing the fan has two advantages , the slower it crosses the coil the more moisture you can draw from it ,with the fan slowed down you don't lift the moisture back into the air stream.And the reheats stop the temperature swinging to much.
Check the reheat's and the reheat setting's ,
Is someone leaving the door open ;)
How well is the room sealed.
Cheers
Stu

[Gideon Beddows]

Although i work for denco, our kit is pretty similar and you need to be looking at heat load.

If the unit has 17 KW of Cooling but only 8KW of Heating then the unit will overcool. Most equipment manufacturers will expect a degree of load in the room to control the de-hum demand. If its an archive room there will never be a heat load.

You need to match the heating load with the cooling load.

If the unit has a hot-gas bypass valve then when the unit approaches Cooling setpoint, you want to start adjusting the valve to allow the hot gas into the coil - thus de-rating the cooling.

Does the unit have thyristor heating? Check the output at 100% load to make sure the output hasnt been adjusted. However, you need some airflow to prevent the klixons tripping at full heating?

If you havnt enough heating to match or better the cooling then buy some oil filled, electric radiators from Argos and position them around the room!?

Hope that helps?